Process for producing a synthesis gas

Abstract

Process for manufacturing a hydrogen-containing synthesis gas from a natural gas feedstock, comprising the conversion of said natural gas into a raw product gas and purification of said product gas, the process having a heat input provided by combustion of a fuel; said process comprises a step of conversion of a carbonaceous feedstock, and at least a portion of said fuel is a gaseous fuel obtained by said step of conversion of said carbonaceous feedstock, and the Wobbe Index of said fuel is increased by a step of carbon dioxide removal or methanation.

The invention claimed is: 
     
       1. A process for manufacturing a hydrogen-containing synthesis gas from a natural gas feedstock including a stage of converting said natural gas feedstock into a raw product gas and purifying said raw product gas, said process includes providing heat input by combustion of a fuel, wherein said process includes producing a gaseous fuel and combusting said gaseous fuel to provide at least part of said heat input to the stage of converting, said process for producing said gaseous fuel comprising:
 a) gasifying a solid or liquid carbonaceous feedstock into a first gaseous product; and 
 b) treating said first gaseous product to obtain said gaseous fuel which is not used as a process gas, said treating including at least one of:
 b1) removing carbon dioxide with a purity of at least 90% molar; or 
 b2) methanation; 
 
 wherein said gaseous fuel has an upper Wobbe Index of at least 14 MJ/Nm 3 . 
 
     
     
       2. The process of  claim 1 , wherein the purity is at least 95%. 
     
     
       3. The process of  claim 1 , wherein the purity is at least 98%. 
     
     
       4. The process of  claim 1 , wherein said step b1) of removing carbon dioxide includes removing a fraction of the carbon dioxide content of a processed gas, said fraction is not greater than 90%, thereby leaving a corresponding residual carbon dioxide in said gaseous fuel. 
     
     
       5. The process of  claim 4 , wherein the fraction is not greater than 75%. 
     
     
       6. The process of  claim 1 , wherein said step b1) is carried out by adsorption of carbon dioxide on a regenerable solid adsorbent. 
     
     
       7. The process of  claim 6 , wherein said adsorption includes regenerable pressure swing adsorption. 
     
     
       8. The process of  claim 1 , wherein said step b2) of methanation is carried out after said step b1) of removing carbon dioxide. 
     
     
       9. The process of  claim 8 , further comprising recovering heat from said step b2) of methanation by generation of steam. 
     
     
       10. The process of  claim 1 , wherein the upper Wobbe Index of said gaseous fuel is at least 19 MJ/Nm 3 . 
     
     
       11. The process of  claim 1 , wherein the upper Wobbe Index of said gaseous fuel is at least 24 MJ/Nm 3 . 
     
     
       12. The process of  claim 1 , wherein said step a) of gasifying is carried out in a fluidized bed. 
     
     
       13. The process of  claim 12 , wherein ash and/or fine particulate matter produced during said step a) of gasifying is subject to a further combustion in a separate boiler. 
     
     
       14. The process of  claim 13 , wherein said separate boiler includes a circulating fluid bed coal boiler. 
     
     
       15. The process of  claim 14 , wherein said separate boiler produces steam and said steam is used in said step a) and/or in said stage of converting said natural gas feedstock and/or in said purification of said raw product gas. 
     
     
       16. The process of  claim 12 , wherein said step a) of gasifying includes moderating a gasification temperature with a moderator, and wherein said moderator is other than water. 
     
     
       17. The process of  claim 16 , wherein said moderator includes nitrogen. 
     
     
       18. The process of  claim 16 , wherein said moderator includes nitrogen, and wherein the moderator is admitted to the gasification process either: i) by a dedicated feed of nitrogen, or ii) together with oxygen by a feed of air or oxygen-enriched air. 
     
     
       19. The process of  claim 1 , wherein the step b) of treating includes:
 i) a step of catalytic hydrolysis of the carbonyl sulfide (COS), thereby producing a gas with a reduced content of carbonyl sulfide and an increased content of hydrogen sulfide (H 2 S); 
 ii) a step of H 2 S separation by via a wash with a liquid solution with affinity to capture H 2 S that produces a sour H 2 S-rich stream and a gas stream with reduced H 2 S content; and 
 iii) feeding the gas stream with reduced H 2 S content to any of step b1 or step b2. 
 
     
     
       20. The process of  claim 19 , wherein said step of H 2 S separation by via a wash with a liquid solution with affinity to capture H 2 S includes an MDEA wash selective for H 2 S over CO 2 . 
     
     
       21. The process of  claim 1 , wherein said carbonaceous feedstock includes at least one of coal, lignite, coal-derived coke, petroleum coke, or heavy fuel oil; and wherein said step of conversion into gaseous fuel is a gasification process.